Issues of Special Interest in Oral Fluid Testing

1. Although oral fluid can be collected under direct supervision and opportunity for sample adulteration is low, measurement of human IgG is recommended for sample validity.

2. To avoid adulteration, supervision of donor for 10-20 min is recommended prior to sampling. The donor should not put anything in his/her mouth during this period.

3. To ensure that positive THC result, using point of care testing device, on an oral fluid specimen is from active exposure, SAMHSA proposes collection of a urine sample along with oral fluid specimen for testing THC metabolite.

4. There are a number of products available on the Internet that guarantee to beat oral fluid drug of abuse tests. There is no scientific evidence that these products work. Using an on-site oral fluid drug screen, Oratect, Wong et al. (79) investigated the effects of various adulterants and foodstuffs. Common foods, beverages, food ingredients, cosmetics and hygienic products were demonstrated not to cause false-positive results when tested 30 min after their consumption. In addition, two commercial adulterant products "Clear Choice Fizzy Flush" and "Kleen Mouthwash" were tested and had no effect in destroying the drug compounds or changing the pH of the oral fluid. Their effect was through washing oral cavity and not different from a common mouthwash. In another study, a series of potential adulterants of oral fluid were evaluated and shown not to interfere in Cozart microplate EIA for opiates (80).

5. Salivary pH ranges from 6.2 to 7.4. Stimulation of oral fluid flow raises pH due to secretion of bicarbonate in oral fluid. This can affect concentration of some drugs in oral fluid. Studies have shown that concentration of cocaine and its metabolites is higher in non-stimulated oral fluid as compared to mechanical stimulation. To avoid these effects, some investigators recommend spitting into a cup, but some donors may find spitting offensive especially when observed.

6. Parent drug is generally present in higher concentrations in oral fluid as compared to urine.

7. Some donors may experience dry mouth and may not be able to provide oral fluid sample.

8. Generally, there is a good correlation between oral fluid and free (active) drug in plasma.

9. Due to a short detection window, if more than 24 h prior notice is given for sample collection, oral fluid is not a specimen of choice.

10. There is significant inter-individual variation for sample volume of oral fluid, and there is no easy on-site method to check sample volume. In a study using 83 normal individuals, the volume ranged from 0.05 to 0.8 mL (68).

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